Methods and apparatuses for shaping a printed circuit board

ABSTRACT

Methods and apparatuses for shaping a corner of a printed circuit board are disclosed. An apparatus in accordance with one embodiment includes a carrier configured to releasably contact a printed circuit board, a curved contact surface positioned to roll against a corner of the printed circuit board. Optionally, another curved contact surface can be positioned to roll against another corner of the printed circuit board. The contact surface can be rotatable relative to the carrier about a rotation axis that is generally parallel to at least a portion of the curved contact surface. The contact surface can be continuous or discontinuous, and can shape the corner of the printed circuit board with a reduced tendency for damage to the printed circuit board. Multiple contact surfaces can be rotatable about different rotation axes.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.10/430,612, filed May 5, 2003, which is incorporated herein by referencein its entirety.

TECHNICAL FIELD

The present application is directed toward methods and apparatuses forshaping printed circuit boards.

BACKGROUND

Printed circuit boards (PCBs) are used widely in the computer industryto support microelectronic devices for removable, electrical coupling toother components. For example, computer motherboards typically includeexpansion slots or sockets configured to receive a PCB that in turncarries microelectronic devices, such as memory chips. The memorycapacity of the computer can be selectively enhanced by coupling the PCB(and, therefore, the memory chips it carries) to the expansion slot.Accordingly, the PCB typically includes electrical PCB contacts that areelectrically connected to the microelectronic devices and thatreleasably connect to corresponding socket contacts when the PCB isinserted into the socket.

One drawback with PCBs is that they can become damaged as they areinserted into the corresponding sockets. For example, the plies orlayers of material forming a PCB can peel away from each other if thePCB is not precisely aligned with the socket during insertion. Onemethod for addressing this drawback has been to bevel the leading edgeof the PCB to ease the entry of the PCB into the socket. For example,the corners at the leading edge of the PCB can be trimmed with sharpblades, or milled to have sloped profiles that slide more easily intothe corresponding sockets.

One drawback with the foregoing beveling approaches has been that theycan create undesirable debris and can waste valuable conductivematerials of the PCB. U.S. Pat. No. 6,368,540 to Morales, assigned tothe assignee of the present application and incorporated herein byreference, addresses this drawback. For example, Morales disclosesrolling a wheel along the corners of the PCB rather than removingmaterial from the corners. The wheel deforms the initially sharp cornersinto beveled surfaces. In a particular embodiment, the corners of thePCB can be beveled by a wheel having a circumferentially extending,V-shaped slot with angled surfaces corresponding to the desired bevelangle for the corners of the PCB. While this approach has beensuccessful for beveling the corners of the PCB without removing materialfrom the corners, the contact between the PCB and the surfaces of thewheel can in some cases create undesirable forces on the PCB.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially schematic, isometric illustration of a PCB priorto being shaped in accordance with an embodiment of the invention.

FIG. 2 is a partially schematic, isometric illustration of an apparatusfor shaping PCBs in accordance with an embodiment of the invention.

FIG. 3 is an end view of a portion of the apparatus shown in FIG. 2.

FIG. 4 is an end view of a PCB after having been shaped in accordancewith an embodiment of the invention.

FIG. 5A is an isometric illustration of a roller having a recess inaccordance with an embodiment of the invention.

FIG. 5B is an isometric illustration of a portion of a PCB after havingbeen shaped with the roller shown in FIG. 5A.

FIG. 6A is an end view of an apparatus configured to shape a PCB inaccordance with another embodiment of the invention.

FIG. 6B is an isometric view of an embodiment of the apparatus shown inFIG. 6A.

DETAILED DESCRIPTION

A. Introduction

The present invention is directed toward methods and apparatuses forshaping printed circuit boards (PCBs). Several specific details of theinvention are set forth in the following description and in FIGS. 1-6Bto provide a thorough understanding of certain embodiments of theinvention. One skilled in the art, however, will understand that thepresent invention may have additional embodiments, and that otherembodiments of the invention may be practiced without several of thespecific features explained in the following description.

An apparatus in accordance with one aspect of the invention includes acarrier having at least one contact portion positioned to releasablycontact a printed circuit board. At least one curved contact surface canbe positioned at least proximate to the carrier and can be rotatablerelative to the carrier about a rotation axis to roll against a cornerof the printed circuit board when the carrier carries the printedcircuit board. The rotation axis can be generally parallel to the curvedcontact surface. In a particular embodiment, another curved contactsurface can be positioned at least proximate to the carrier and can berotatable relative to the carrier about another rotation axis differentthan the first rotation axis. The other contact surface can bepositioned to roll against another corner of the printed circuit boardwhen the carrier carries the printed circuit board. Accordingly, thecontact surface(s) can bevel or otherwise shape the corner(s) of theprinted circuit board.

In further aspects of the invention, the contact surface can form aportion of a roller, and the contact surface can be generally continuousor can have a discontinuity, for example, a recess. In still furtheraspects of the invention, first and second contact surfaces can form acontact surface pair, and at least one of the carrier and the contactsurface pair can be movable relative to the other along a motion axisextending between the rotation axes about which the contact surfacesrotate.

A method for shaping a corner of a printed circuit board in accordancewith another aspect of the invention includes positioning a corner ofthe printed circuit board against a curved contact surface. The methodcan further include changing a shape of the corner as at least one ofthe contact surface and the corner moves relative to the other while thecontact surface rotates about a rotation axis, with the rotation axisbeing generally parallel to at least a portion of the curved contactsurface. In a particular embodiment, another corner of the printedcircuit board is positioned against another curved contact surface and ashape of the other corner is changed as at least one of the othercontact surface and the other corner moves while the other contactsurface rotates about another (different) rotation axis.

In further aspects of the invention, the printed circuit board caninclude a first face, a second face, and an intermediate surface betweenthe first and second faces, with a first corner positioned between thefirst face and the intermediate surface, and with a second cornerpositioned between the second face and the intermediate surface. Themethod can further include aligning a first rotation axis of a firstcurved surface at about 30 degrees relative to the first face, andaligning a second rotation axis of a second curved surface at about 30degrees relative to the second face.

B. Apparatuses and Methods in Accordance With Embodiments of theInvention

FIG. 1 is a partially schematic, isometric illustration of a PCB 100suitable for being shaped in accordance with an embodiment of theinvention. In one aspect of this embodiment, the PCB 100 can include asubstrate 101 formed from sandwiched layers of conductive andnonconductive materials. Accordingly, the substrate 101 can haveopposing faces 103 (shown in FIG. 1 as a first face 103 a and a secondface 103 b behind the first face 103 a). A downwardly facingintermediate surface 104 is positioned between the faces 103 a, 103 b toform two corners 105 (shown as a first corner 105 a and a second corner105 b). The corners 105 can initially be generally sharp (as shown inFIG. 1) and can subsequently be beveled using methods and apparatuses inaccordance with embodiments of the invention.

In one embodiment, the first and second faces 103 a, 103 b can eachcarry devices 102, such as memory chips, processors, or othermicroelectronic devices. The devices 102 are electrically connected tocontact arrays 110 with traces (not visible in FIG. 1) positioned at orbelow the surfaces of the faces 103. Each contact array 110 can includea conductive material 112 (such as gold) formed into a plurality ofcontacts 111. Each contact 111 can include a tie bar 113 that extends tothe first corner 105 a. Accordingly, the tie bars 113 can provideelectrical continuity with the contacts 111 during the platingoperations typically used to form the contacts 111. In one aspect ofthis embodiment, the PCB 100 can include two contact arrays 110separated by an intermediate, contactless portion 114. In otherembodiments, the PCB 100 can include a single contact array 110 or morethan two contact arrays 110. In any of these embodiments, the PCB 100can be received in a socket 115 which can have corresponding contactreceptacles 116. The contact receptacles 116 can include socketterminals or contacts (not visible in FIG. 1) that releasably,electrically connect with the PCB contacts 111.

FIG. 2 is a partially schematic, isometric illustration of an apparatus120 configured to shape the corners 105 of a PCB 100 (for example, thePCB 100 described above with reference to FIG. 1). For purposes ofillustration, a portion of the PCB 100 is shown broken away in FIG. 2.In one embodiment, the apparatus 120 can include a carrier 130configured to releasably carry the PCB 100 so that the corners 105 bearagainst two contact surfaces 142 (shown as a first contact surface 142 aand a second contact surface 142 b). Each contact surface 142 can rotateabout a different axis while the contact surfaces 142 pass into and outof contact with the PCB 100, as described in greater detail below.

In one embodiment, the contact surfaces 142 can form a contact surfacepair, and each contact surface 142 can be carried by a roller 141.Accordingly, the apparatus 120 can include two rollers 141, shown as afirst roller 141 a (carrying the first contact surface 142 a) and asecond roller 141 b (carrying the second contact surface 142 b). Therollers 141 can be rotatably mounted to a roller mount 140, positionedproximate to the carrier 130. In one aspect of this embodiment, thefirst roller 141 a rotates about a first rotation axis 143 a, and thesecond roller 141 b rotates about a second rotation axis 143 b,different than the first rotation axis 143 a. In a particularembodiment, each contact surface 142 a, 142 b is curved and concentricwith the respective rotation axis 143 a, 143 b. In other embodiments,the contact surfaces 142 can have different arrangements. For example,the contact surfaces 142 can be carried by belts or treads that extendaround a pair of support wheels. In any of these embodiments, thecontact surfaces 142 can be positioned to engage the corners 105 of thePCB 100 while the PCB 100 is carried by the carrier 130. Accordingly,the contact surfaces 142 can include materials selected to withstandrelatively high compressive forces. Such materials include hardenedsteel.

In one aspect of an embodiment shown in FIG. 2, the carrier 130 caninclude a contact portion 132 for releasably contacting the PCB 100. Inone embodiment, the contact portion 132 includes two grippers 131, eachof which engages an oppositely facing end surface 108 a, 108 b of thePCB 100. In a further aspect of this embodiment, the apparatus 120 caninclude an actuator system 125 having a motion actuator 121 coupled tothe carrier 130 to move the PCB 100 relative to the contact surfaces142. For example, the carrier 130 can move the PCB 100 relative to theroller mount 140 along a motion path 124 that is generally parallel withthe corners 105. In another embodiment, described in greater detailbelow with reference to FIG. 6, the roller mount 140 can translate alongthe motion path 124 while the PCB 100 remains stationary. In still afurther embodiment, the motion actuator 121 can translate the PCB 100 inone direction while the roller mount 140 translates in the oppositedirection. In any of these embodiments, the rollers 141 need not beactively driven, but can rotate freely as a result of the relativemotion between the PCB 100 and the contact surfaces 142. Accordingly,each roller 141 can rotate independently of the other, but will tend torotate simultaneously with the other when both rollers 141 engage thePCB 100.

In another aspect of an embodiment shown in FIG. 2, the motion actuator121 can also move the carrier 130 relative to a tray 123, which supportsa plurality of the PCBs 100. Accordingly, the carrier 130 can operate inan automatic or semi-automatic manner to (1) pick an unshaped PCB 100from the tray 123, (2) shape the PCB 100 by contacting it with thecontact surfaces 142, and (3) return the shaped PCB 100 to the same or adifferent tray 123 after shaping. In other embodiments, the PCB 100 canbe loaded, unloaded and/or moved manually.

In any of the foregoing embodiments, the edges 105 of the PCB 100 bearagainst the contact surfaces 142 as the PCB 100 and the contact surfaces142 move relative to each other. Accordingly, the apparatus 120 canapply a force to the corners 105 in a direction generally normal to themotion path 124 as the PCB 100 bears against the contact surfaces 142.In one aspect of this embodiment, the roller mount 140 can be coupled toa normal force actuator 122 a or other device to force the rollers 141upwardly against the PCB 100 along a force axis 126. For example, in aparticular aspect of this embodiment, the normal force actuator 122 acan apply an upward force of about 20 pounds. In other embodiments, thenormal force actuator 122 a can apply forces having other values,depending on factors that include but are not limited to the compositionand size of the PCB 100, and the orientation of the rotation axes 143.

In another embodiment, the carrier 130 can be coupled to a normal forceactuator 122 b or another device that forces the PCB 100 downwardlyagainst the rollers 141. In still further embodiments, the normal forceactuators 122 a, 122 b can be eliminated, for example, when the combinedweight of the carrier 130 and the PCB 100 provides sufficient bearingforce between the corners 105 and the contact surfaces 142.

FIG. 3 is a partially schematic, end view of a portion of the apparatus120 described above with reference to FIG. 2. As shown in FIG. 3, eachcontact surface 142 a, 142 b can contact a corresponding one of theprinted circuit board corners 105 a, 105 b, respectively. As is alsoshown in FIG. 3, the first roller 141 a can rotate about the firstrotation axis 143 a independently of the rotation of the second roller141 b about the second rotation axis 143 b. For example, as the rollers141 and the PCB 100 translate relative to each other along the motionaxis 124, the first roller 141 a can rotate counterclockwise about thefirst rotation axis 143 a (as indicated by arrow F), and the secondroller 141 b can rotate clockwise about the second rotation axis 143 b(as indicated by arrow G).

FIG. 4 is a partially schematic, end view of a portion of the PCB 100after undergoing a shaping process in accordance with an embodiment ofthe invention. In one aspect of this embodiment, the PCB 100 can includebeveled portions 106 (as shown as a first beveled portion 106 a and asecond beveled portion 106 b). The beveled portions 106 can be symmetricwith respect to each other so that a first angle A between the plane ofthe first beveled portion 106 a and the first face 103 a is at leastapproximately the same as a second angle B between the plane of thesecond beveled portion 106 b and the second face 103 b. In anotherembodiment, the first angle A can be different than the second angle B.In either embodiment, the first and second angles A, B can have valuesof from about 15 degrees to about 60 degrees. In a particularembodiment, the first and second angles A, B can have values of fromabout 20 degrees to about 45 degrees, and in a further particularembodiment, the first and second angles A, B can each have a value ofabout 30 degrees. In any of these embodiments, each beveled portion 106can extend away from the intermediate surface 104 of the PCB 100 by adistance D. In one embodiment, the distance D can be from about 0.001inch to about 0.020 inch, and in a particular embodiment, the distance Dcan vary from about 0.002 inch to about 0.010 inch. In any of theseembodiments, the beveled portions 106 can include conductive materials,non-conductive materials, or both conductive and non-conductivematerials of the PCB 100.

One feature of an embodiment of the apparatus 120 described above withreference to FIGS. 2 and 3 is that the first contact surface 142 arotates about a different rotation axis than does the second contactsurface 142 b as the apparatus 120 shapes the corners 105 of the PCB100. For example, in a particular aspect of this embodiment, a firstline 144 a (FIG. 3) extending at least approximately perpendicularly tothe first contact surface 142 a and the surface of the first beveledportion 106 a is also at least approximately perpendicular to the firstrotation axis 143 a. A second line 144 b (FIG. 3) extending at leastapproximately perpendicularly to the second contact surface 142 b andthe surface of the second beveled portion 106 b is also at leastapproximately perpendicular to the second rotation axis 143 b. Viewed inanother manner, the rotation axis 143 for each contact surface 142 canbe generally parallel to at least a portion of the contact surface 142and to at least a portion of the plane of the corresponding beveledportion 106. As a result, the force applied by each contact surface 142to the respective corner 105 can have a reduced tangential componentwhen compared with other methods for beveling PCB corners.

An advantage of the foregoing feature is that the contact surfaces 142are less likely to strip material from the PCB 100 or cause layers ofthe PCB 100 to delaminate. For example, embodiments of the apparatus 120can be less likely than existing apparatuses to damage the tie bars 113(FIG. 1) of the PCB 100 during the beveling process. Accordingly, PCBs100 shaped with embodiments of the apparatuses and methods describedabove can be more likely to have uniformly beveled corners 105. As aresult, the PCBs 100 can be more smoothly and reliably received by thesockets 115 (FIG. 1).

In other embodiments, the apparatus 120 described above can have otherarrangements. For example, the apparatus 120 can include a singlecontact surface 142 that rotates about a single rotation axis 143 tobevel or otherwise shape one corner 105. In one aspect of thisembodiment, the opposite corner can be supported with a block or otherstructure to prevent or at least restrict the PCB 100 from bending whilethe contact surface 142 engages the corner 105. Such an arrangement canbe suitable when beveling a single corner 105 of the PCB 100 providesthe desired ease of insertion as the PCB 100 is received in the socket115 (FIG. 1). An advantage of this arrangement is that the apparatus canbe simplified because the number of contact surfaces 142 can be reduced.

In other embodiments, the apparatus 120 described above can have stillfurther arrangements. For example, FIG. 5A illustrates a roller 541(suitable for use with embodiments of the apparatus 120 described above)having a contact surface 542 with a recess 544 or other discontinuity.FIG. 5B illustrates a portion of a PCB 100 having corners 105 shaped bytwo rollers 541 generally similar to the one shown in FIG. 5A. Referringto FIGS. 5A and 5B together, the roller 541 can shape different portionsof the PCB corner 105 in different manners. In a particular embodiment,the roller 541 can provide a beveled portion 506 where the contactsurface 542 engages the corner 105, and an unbeveled portion 507 wherethe recess 544 aligns with the corner 105. In other embodiments, theroller 541 can have other discontinuous contact surfaces 542 and/orother patterns and/or arrangements of recesses 544.

In any of the foregoing embodiments, the unbeveled portion 507 can beused to align the PCB 100 when the PCB is inserted into a correspondingsocket. For example (referring now to FIG. 1), the PCB 100 can include aplurality of contact arrays 110 separated by a contactless portion 114,and the socket 115 can include a corresponding plurality of contactreceptacles 116 separated by a gap 117. An embodiment of the roller 541described above with reference to FIG. 5A can bevel the contact arrays110 and leave the contactless portion 114 unbeveled. The contactreceptacles 116 can be shaped to selectively receive the beveled contactarrays 110, and the gap 117 can be shaped to selectively receive theunbeveled contactless portion 114. Accordingly, the PCB 100 will seatproperly only when the contact arrays 110 are aligned with thecorresponding contact receptacles 116, and the contactless portion 114is properly aligned with the gap 117. In other embodiments, the roller541 can be configured to provide other beveled and/or unbeveled patternson the PCB 100. For example, the roller 541 can include a plurality ofrecesses to provide an unbeveled portion between each contact 111 of thecontact arrays 110. In still another embodiment, the contact surface 542can be convex (e.g., crowned) or concave, or can have othercross-sectional shapes.

FIG. 6A is a partially schematic end view of an apparatus 620 configuredto shape the edges of the PCB 100 in accordance with another embodimentof the invention. FIG. 6B is an isometric view of an embodiment of theapparatus 620. In one aspect of the embodiment shown in FIGS. 6A-6B, theapparatus 620 includes a carrier 630 configured to support the PCB 100,and a roller mount 640 configured to support rollers 641 a, 641 b. In aparticular aspect of this embodiment, the carrier 630 is positionedbelow the roller mount 640. In another aspect of this embodiment, thecarrier 630 can be manually loaded with the PCB 100. In still a furtheraspect of this embodiment, the roller mount 640 can translate along amotion path 624 relative to the PCB 100. The first and second rollers641 a, 641 b can rotate about different rotation axes 643 a, 643 b in amanner generally similar to that described above with reference to FIGS.2 and 3. Accordingly, embodiments of the apparatus 620 described abovewith reference to FIG. 6A-6B can provide shaped PCB corners havingcharacteristics generally similar to those described above withreference to FIGS. 2-5B.

From the foregoing, it will be appreciated that specific embodiments ofthe invention have been described herein for purposes of illustration,but that various modifications may be made without deviating from thespirit and scope of the invention. Accordingly, the invention is notlimited except as by the appended claims.

1. A method for shaping a corner of a printed circuit board, comprising:positioning a corner of a printed circuit board against a curved contactsurface; and changing a shape of the corner as at least one of thecontact surface and the corner moves relative to each other while thecontact surface rotates about a rotation axis, the rotation axis beinggenerally parallel to at least a portion of the curved contact surface.2. The method of claim 1 wherein the curved contact surface includes acurved first contact surface that rotates about a first rotation axis,and wherein the corner includes a first corner, and wherein the methodfurther comprises: positioning a second corner of the printed circuitboard against a curved second contact surface; and changing a shape ofthe second corner as at least one of the second contact surface and thesecond corner moves relative to the other while the second contactsurface rotates about a second rotation axis different than the firstrotation axis.
 3. The method of claim 1 wherein changing a shape of thecorner includes beveling the corner to form a beveled plane, and whereinthe contact surface rotates about a rotation axis generally parallel tothe beveled plane.
 4. The method of claim 1 wherein positioning a cornerof a printed circuit board against a contact surface includespositioning the corner against a portion of a roller.
 5. The method ofclaim 1, comprising moving at least one of the printed circuit board andthe contact surface relative to the other along a motion axis alignedgenerally parallel to the corner while the contact surface contacts theprinted circuit board.
 6. A method for shaping a corner of a printedcircuit board, comprising: positioning a first corner of a printedcircuit board against a curved first contact surface; positioning asecond corner of the printed circuit board against a curved secondcontact surface; changing a shape of the first corner as the firstcontact surface and the first corner move relative to the other whilethe first contact surface rotates about a first rotation axis; andchanging a shape of the second corner as the second contact surface andthe second corner move relative to each other while the second contactsurface rotates about a second rotation axis different than the firstrotation axis.
 7. The method of claim 6 wherein positioning a firstcorner of a printed circuit board against a first contact surfaceincludes positioning the first corner against a portion of a firstroller and wherein positioning a second corner of a printed circuitboard against a second contact surface includes positioning the secondcorner against a portion of a second roller.
 8. The method of claim 6wherein the first and second contact surfaces form a contact surfacepair and wherein the method further comprises moving at least one of theprinted circuit board and the contact surface pair relative to the otheralong a motion axis aligned generally parallel to the first and secondcorners while the first and second contact surfaces contact the printedcircuit board.
 9. The method of claim 6 wherein positioning a firstcorner includes positioning a first conductive portion of the printedcircuit board against the first contact surface.
 10. The method of claim6 wherein positioning a first corner includes positioning the firstcorner against a generally continuous first surface.
 11. The method ofclaim 6 wherein positioning a first corner includes positioning thefirst corner against a discontinuous first surface.
 12. The method ofclaim 6 wherein the first contact surface has at least one recess, andwherein changing a shape of the first corner includes changing a shapeof the first corner where the first surface engages the first corner butnot where the at least one recess aligns with the first corner.
 13. Themethod of claim 6 wherein the first and second contact surfaces form acontact surface pair and wherein the method further comprises forcing atleast one of the printed circuit board and the contact surface pairtoward the other.
 14. The method of claim 6 wherein the printed circuitboard has a first face, a second face and an intermediate surfacebetween the first and second faces, with the first corner positionedbetween the first face and the intermediate surface, and with the secondcorner positioned between the second face and the intermediate surface,and wherein the method further comprises: aligning the first rotationaxis of the first contact surface at about 30 degrees relative to thefirst face; and aligning the second rotation axis of the second contactsurface at about 30 degrees relative to the second face.
 15. The methodof claim 6 wherein the printed circuit board has a first face, a secondface and an intermediate surface between the first and second faces,with the first corner positioned between the first face and theintermediate surface, and with the second corner positioned between thesecond face and the second intermediate surface, and wherein the firstand second contact surfaces form a contact surface pair, and wherein themethod further comprises: aligning the first rotation axis of the firstcontact surface at about 30 degrees relative to the first face; aligningthe second rotation axis of the second contact surface at about 30degrees relative to the second face; and applying a force of about 20pounds to the printed circuit board along an axis approximately midwaybetween the first and second rotation axes.
 16. A method for shaping anedge of a printed circuit board, comprising: positioning a first cornerof a printed circuit board against a curved first contact surface of afirst roller; positioning a second corner of the printed circuit boardagainst a curved second contact surface of a second roller, the firstand second rollers forming a roller pair; moving the printed circuitboard and the roller pair relative to each other along a motion axisaligned generally parallel to the first and second corners; changing ashape of the first corner as the first contact surface and the firstcorner move relative to the other while the first roller rotates about afirst rotation axis; changing a shape of the second corner as the secondcontact surface and the second corner moves relative to the each otherwhile the second roller rotates about a second rotation axis differentthan the first rotation axis; applying a force to the first corner alonga first force axis positioned between the first and second rotationaxes; and applying a force to the second corner along a second forceaxis positioned between the first and second rotation axes, the secondforce axis being generally parallel to the first force axis.
 17. Themethod of claim 16 further comprising rotating the first and secondrollers simultaneously.
 18. The method of claim 16 wherein the printedcircuit board has a first face, a second face and an intermediatesurface between the first and second faces, with the first cornerpositioned between the first face and the intermediate surface, and withthe second corner positioned between the second face and theintermediate surface, and wherein the method further comprises: aligningthe first rotation axis of the first contact surface at about 30 degreesrelative to the first face; and aligning the second rotation axis of thesecond contact surface at about 30 degrees relative to the second face.